As we have seen in question 2,
the conclusion that abrupt climate changes have occurred in the past is almost
impossible to avoid. Their timing, however, is rather difficult to pin down,
due to the inherent imprecision of geochemical dating methods (decay of radioactive
elements such as carbon 14 or uranium series). Nonetheless, the analysis of
annually banded records (ice cores, corals, tree-rings, or speleothems) has
firmly established the rapid rate of these changes.

The ubiquitous character of certain events further confirms
their importance: "the Younger Dryas and a large number of abrupt changes
during the last ice age called Dansgaard/Oeschger events (23 abrupt changes
into a climate of near-modern warmth and out again, during the last glacial
period) have been corroborated in multiple ice cores from Greenland, Antarctica
and tropical mountains, marine sediments from the North Atlantic Ocean, the
tropical Atlantic, eastern Pacific, and Indian Oceans, and from various records
on land. Other, smaller abrupt changes have been linked to societal
disruptions. Evidence for some of these events are more regional in nature,
and points to far less dramatic changes. However, these events did occur so
rapidly and unexpectedly that human or natural systems had difficulty adapting
to them - the second definition of abrupt climate change." (source: NOAA Facts Sheet)

Thus, while we like to find evidence of large events in many
distant locations, local changes can be instructive examples of abrupt climate
change, if properly dated.